It is quite common to install a continuous tubular flow conductor, or casing, into a well bore in order to ensure long term integrity, serviceability of the well, and to increase the kinds and types of production enhancing treatments that may be performed within the well bore over the life of the well. Generally, casing is made of tubular members and joints made of steel, iron, polymeric materials such as polyvinyl chloride, or glass fiber reinforced thermosetting epoxy resin, with steel being the most common for use in oil and gas, and in some water wells. The steel casing is secured within the well bore by pumping cement downward through the casing, out the bottom thereof, and then the cement is forced upward between the exterior of the casing and the well bore. After the cement has been given time to cure, or set-up, the casing, and adjacent cement, is usually perforated at preselected locations so that pay zones at various depths can be accessed for producing oil, gas, or water therefrom.
Perforation of continuous casing is usually accomplished by setting off directional explosive charges or by hydraulic jetting. Perforation by explosive charges is carried out by lowering specially designed apparatus downhole to the desired depth at which the pay zone exists. Upon the explosive carrying apparatus being located, explosives are discharged which blasts holes through the casing allowing the adjacent formation to be in communication with the interior of the casing.
Perforation by hydraulic jetting is accomplished by cutting holes, or slots, in the casing by lowering downhole tools referred to as hydraulic jetting tools, or water jetting tools, to the desired total depth and relative azimuth. Upon placing the hydrajetting tool at the desired depth and orientation, high pressure liquid, such as water at a delivered pressure of a few thousand psi to as possibly as high as 15,000 psi (150-1050 kg/cm.sup.2) is pumped downhole to the tool which directs the pressurized fluid to a jet nozzle that expels the high pressure fluid at the wall of the casing thereby cutting a hole, or slot, in not only the casing but in the cement and to a certain extent the adjacent formation. It is also well known that abrasive particle laden fluids may be used for hydraulic jetting in order to increase, or alter, the cutting capability and/or decrease the amount of time needed to perforate casings. Representative compatible hydraulic jetting apparatus assigned to the assignee of the present invention, are disclosed in U.S. Pat. Nos. 5,249,628, 4,346,761; 3,958,641; 3,892,274; and 3,145,776 and such references are specifically incorporated into the present disclosure.
A shortcoming with priorly known methods of hydraulic jetting, especially when employing abrasive particle laden fluids, is that the abrasives, which are typically particles of sand, or silica, steel shots, or garnet must be flushed from the casing prior to initiating production or performing other well treatments to eliminate unwanted sand, or other abrasive particles. Such flushing can often be a time consuming and difficult process and if not done adequately, the residual abrasive particles can and often lead to jamming or damaging of other tools to be placed and operated downhole. Thus, an object of the present invention is to fulfill a need for a method of cutting steel well casings, both cemented and uncemented, while minimizing the difficulty and amount of time required for cleaning, or flushing, the structure, or site, in which the hydra-jet cutting takes place, especially when the hydra-jetting is conducted in blind, physically remote areas such as in a vertical or horizontal well bore.
Another object of the present invention is to provide a method of cutting metal and non-metal substrates with hydraulic jet cutting tools, whether performed above or below the surface.
A further object of the present invention is to provide a method of cutting metal and non-metal subtrates with hydraulic jet cutting tools which essentially eliminates the existence of residual abrasive particles in the adjacent work area.
These and other objects will be accomplished by the present invention as discussed and disclosed herein.